I would run memtest, and also check your system temps in the bios hardware monitor for gradual changes. MBM version 5.370 will list the temps for the cpu and mobo in the lower right area of your screen.
ya, check system temps. intel does a good job throttling down when they get hot, but amd isn't too good with that. they may be getting better, but i believe it was around the 2500 generation that THG used in an overheating experiment when it just exploded from heat. intels will just slow down to a halt, amds shut down altogether.
I've similar problem with random resettings, right after a BSOD. (Sometimes it just BSOD without resetting.) This happens when I upgraded from 512M RAM (256M x 2) to 1G RAM (256 x 4) - all running at DDR400. I have tried trouble shooting with power supply, reformat/reinstall WinXP, re-arrange memory in different slot, etc.,and problem still exist.
Then I found this FAQ within Gigabyte site regarding memory issue:
"Q: My motherboard provides four DIMM slot for expansion. But, when I install 4xDDR400 memory modules on this MB, while BIOS POST, the board only recognizes my memory mdoules as DDR266. Please fix the problem with new version BIOS.
A: Based on nVIDIA chipset specification, the motherboard you have only support 3 DIMM slots officially. When a MB comes with GIGABYTE unique memory H/W deisgn, the board you have can provide the extra DIMM slot and make users get better flexibility on H/W installation/expansion. But, because the quality of memory modules in retail market is uneven, thus, when you install 4xDDR400 memory modules on the motherboard, our MB BIOS will decrease memory speed to make sure most system will bootup properly."
So I guess try down the memory speed a bit to see if that helps. I'm going to try that tonight...